Urotensin II (UTS2) encodes a 11 amino acid mature peptide that binds to the orphan G protein-coupled receptor, GPR-14 (renamed urotensin 2 receptor, UTS2R) [Ames et al., 1999, Nature 401: 282-286]. Recent studies have indicated that both UTS2 and/or UTS2R have significant impacts on insulin resistance [Langham et al., 2004, Am J Kidney Dis. 44: 826-831; Suzuki et al., 2004, Peptides 25: 1803-1808 and Ong et al., 2006, Peptides 27: 1659-1667], which represents a core pathological character of patients with type 2 diabetes mellitus and obesity. For example, in Hong Kong Chinese, the GGT haplotype (-605G, 143G and 3836T) in the UTS2 gene is associated with higher plasma level of urotensin 2 and insulin, and higher homeostasis model assessment of insulin resistance index and beta-cell function, while the AC haplotype (-1640A and -8515C) in the UTS2R gene has a higher amount of plasma glucose 2 h after a 75 g oral glucose load [Ong et al. Peptides. 2006; 27(7):1659-67]. In human diabetic tissue, Langham and colleagues [Am J Kidney Dis. 2004; 44(5):826-3 1] found that expression of both UTS2 and UTS2R are increased 45- and almost 2,000-fold in comparison to control nephrectomy tissue, respectively (P<0.0001) using quantitative real-time polymerase chain reaction. In the healthy rat, infusion of synthetic rat urotensin 2 inhibits both insulin release induced by glucose and insulin responses induced by carbachol, glucagon-like peptide-1, and a calcium channel agonist [Silvestre et al. Eur J Endocrinol. 2004; 151(6):803-9]. However, in streptozotocin-induced diabetic rats, long-term treatment with palosuran, a UTS2R antagonist, improved survival, increased insulin, and slowed the increase in glycemia, glycosylated hemoglobin, and serum lipids [Clozel et al. J Pharmacol Exp Ther. 2006; 316(3): 1115-21]. Therefore, the urotensin 2 system plays a unique role both in insulin secretion and in the renal complications of diabetes.
Studies have shown that the fat droplets accumulated in human skeletal muscle are a major contributor to insulin resistance [Goodpaster & Wolf, Pediatr Diabetes. 2004; 5(4):219-26]. For example, in male Pima Indians, negative relationships were found between amounts of triglyceride in skeletal muscle and physiological and supraphysiological insulin levels, and nonoxidative glucose disposal (r=−0.44−−0.53, P<0.01) [Pan et al. Diabetes. 1997; 46:983-8]. In a European population, muscle lipid was correlated with percent body fat (r=0.50, p=0.028), waist:hip ratio (r=0.74, p<0.001), visceral fat (r=0.62, p=0.004) and insulin sensitivity (r=−0.53, p=0.016) [Forouhi et al. Diabetologia. 1999; 42(8):932-5]. In beef cattle, fat accumulation in muscle is usually measured as marbling, which describes the appearance of white flecks or streaks of fat between the muscle fibers. Therefore, the objective of the present study was to determine whether both UTS2 and UTS2R genes contribute to carcass, fat deposition and fatty acid composition in beef cattle.
There is a need for methods that allow relatively easy and more efficient selection and breeding of farm animals that have an advantage for an inheritable trait of beef marbling score (BMS), ribeye area (REA), amounts of saturated (rSFA), monounsaturated (rMUFA) and polyunsaturated fatty acids (rPUFA), Δ9 desaturase activities (R1=14:1 to 14:0; R2=16:1 to 16:0; R3=18:1 to 18:0), conjugated linoleic acid (CLA) and cholesterol (CHOL) . The economic significance of the use of genetic markers that are associated with specific economically important traits (especially carcarss and meat quality traits that are hard to measure) in livestock through marker-assisted selection cannot therefore be over-emphasized.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.